ORDER

JAMES P. O'HARA, Magistrate Judge.

This employment discrimination case comes before the court on the motion of the plaintiff, Lisa McCants, for relief from the directive in the Amended Scheduling Order1 that she serve an expert-witness disclosure, in compliance with Fed. R. Civ. P. 26(a)(2)(C), for her treating physician, Vinoya K. Koduri, M.D. (ECF No. 42). Plaintiff states Dr. Koduri "will testify based upon his personal observations based on person [sic] knowledge, including treatment of Ms. McCants," and not as an expert witness.2 Defendant Correct Care Solutions, LLC, does not oppose the motion to the extent Dr. Koduri will testify only as a lay witness, but notes that if plaintiff plans to use Dr. Koduri "to testify as to the diagnosis and causation of her purported hypertension and anxiety," such testimony would fall in the realm of expert testimony requiring a Rule 26(a)(2)(C) summary disclosure.3 As discussed below, plaintiff's motion is granted, but with a caution.

Fed. R. Civ. P. 26(a)(2)(A) requires a party "to disclose to the other parties the identity of any witness it may use at trial to present evidence under Federal Rule of Evidence 702, 703, or 705." In 2010, sub-section (C) was added to Rule 26(a)(2) specifically to address non-retained witnesses, such as treating physicians, who "may both testify as a fact witness and also provide expert testimony."4 Rule 26(a)(2)(C) eliminates the requirement of such "hybrid" witnesses to file a detailed written expert report5 and instead requires only a written disclosure stating "the subject matter on which the witness is expected to testify" and "a summary of the facts and opinions to which the witness is expected to testify." Since the addition of sub-section (C), it is typical for plaintiffs to file a written disclosure for treating physicians they intend to call as witnesses.6

Plaintiff correctly points out, however, that the Tenth Circuit recognized in Guerrero v. Meadows that a "treating physician does not need to be certified as an expert witness and may testify as a lay witness [under Fed. R. Evid. 701] `if he or she testifies about observations based on personal knowledge, including the treatment of the party.'"7 Thus, if plaintiff truly wishes to offer only Dr. Koduri's lay opinion, then plaintiff is correct that she need not produce a Rule 26(a)(2)(C) disclosure.

The court, however, cautions plaintiff that this is a risky position to take. Without a Rule 26(a)(2)(C) disclosure, it is very possible that the presiding judge will not permit Dr. Koduri to testify about the cause of plaintiff's purported hypertension and anxiety. Under Rule 701, opinion lay testimony is testimony that is "rationally based on the witness's perception," and (at least since the adoption of subsection (c) in 2000) not "based on scientific, technical, or other specialized knowledge within the scope of Rule 702."8 At least one court has recognized that "the Tenth Circuit has not defined the bounds of permissible testimony for a treating physician as a lay witness,"9 but concluded "opinions regarding diagnosis of a medical condition are almost always expert testimony, because diagnosis requires judgment based on scientific, technical, or specialized knowledge in almost every case."10 Should plaintiff wish to reconsider her position, the court grants her until September 11, 2017, to serve a Rule 26(a)(2)(C) disclosure for Dr. Koduri.

IT IS SO ORDERED.